Chapter 16 - Ventricular System Flashcards
The ventricular system is composed of 4-fluid filled cavities within the brain namely:
(1) right and left lateral ventricles - #2
(2) third ventricle
(3) fourth ventricle
What happens when the arachnoid does not follow the surface of the brain closely in certain situations?
The subarachnoid space expands to form various dural sacs, such as the cerebellomedullary cistern, pontine cistern, and interpeduncular cistern.
Where does the subarachnoid space end below?
The subarachnoid space invests the cauda equina and ends below at the level of the interval between the second and third sacral vertebrae.
the subarachnoid space extends beyond the spinal cord becomes part of the cauda equina
volume of CSF
CSF is a clear, colorless fluid that posseses inorganic salts similar to composition of the blood plasma
150 mL
CSF Composition
Memorize
CSF glucose content is half that of blood; only a trace of protein; very few cell - mostly lymphocytes
What is the normal CSF pressure in the lateral recumbent position?
The normal CSF pressure, as measured by spinal tap, is about 60 to 150 mm of water in the lateral recumbent position.
Which of the following can raise the CSF pressure as measured by spinal tap?
A) Lying down in a lateral recumbent position
B) Deep breathing
C) Compressing the internal carotid arteries
D) Straining, coughing, or compressing the internal jugular veins in the neck
Answer: D) Straining, coughing, or compressing the internal jugular veins in the neck can raise the CSF pressure as measured by spinal tap.
What is the significance of the constant CSF pressure?
A) It helps to remove waste products from the brain and spinal cord
B) It helps to protect the brain and spinal cord from physical damage
C) It allows for the normal functioning of the nervous system
D) It prevents infections from entering the brain and spinal cord
Answer: C) It allows for the normal functioning of the nervous system. The constant CSF pressure helps to maintain a stable environment for the brain and spinal cord, which is crucial for their normal functioning. Any changes in pressure can have serious consequences for the health of these organs.
CSF Functions
CSF (1) production rate and (2) turn over time
(1) 0.5 mL/min
(2) 5 hrs
Is CSF production pressure-regulated, and what happens if reabsorption mechanisms are obstructed?
A) CSF production is pressure-regulated like blood pressure, and it stops if reabsorption mechanisms are obstructed.
B) CSF production is not pressure-regulated like blood pressure, and it continues to be produced even if reabsorption mechanisms are obstructed.
C) CSF production is pressure-regulated like blood pressure, and it continues to be produced even if reabsorption mechanisms are obstructed.
D) CSF production is not pressure-regulated like blood pressure, and it stops if reabsorption mechanisms are obstructed.
Answer: B) CSF production is not pressure-regulated like blood pressure, and it continues to be produced even if reabsorption mechanisms are obstructed. This can lead to an accumulation of CSF, which can cause increased pressure within the skull and potentially lead to serious neurological symptoms
Choroid plexus layers
**
(1) core vascular connective tisse
(2) cuboidal epithelium of ependyma - free surfaces with microvilli
**
(3) ventricular lumen
(4) capillary endothelium
(5) basement membrane
(6) surface epithelium - fenestrated and permeable to large molecules
Formation of CSF mainly at
choroid plexuses of the lateral, third, and fourth ventricle
CSF Circulation
1) secretion from the choroid plexuses in the ventricles
2) lateral ventricles > interventricular foramina > third ventricle
3) third ventricle > cerebral aqueduct > fourth ventricle
4) movement is aided by the arterial pulsations of the choroid plexuses and by the cilia on the ependymal cells lining the ventricles
5) to the median aperture & lateral foramina > subarachnoid space
6) movement is assisted by pulsations of the cerebral arteries, spinal arteries, & movements of the vertebral column
CSF not only bathes the ependymal and pial surfaces of the brain and spinal cord but also penetrates the nervous tissue along the blood vessels
Connects the lateral ventricles and the third ventricle
Interventricular foramina
aka Foramen of Monro
This opening lies in the anterior part of the medial wall of the ventricle.
Bounded:
(1) Anteriorly by the anterior column of the fornix
(2) Posteriorly by the anterior end of the thalamus
Connects the third ventricle to the 4th ventricle
cerebral aqueduct
aka aqueduct of Sylvius
the fourth ventricle is continuous with ()
the central canal of the spinal cord
A small dilatation at the inferior end of the spinal cord’s central canal
terminal ventricle
ventricles are lined throughout with (1) and are filled with (2)
(1) ependyma
(2) CSF
the ventricles are developmentally derived from
the cavity of the neural tube
The lateral ventricles are a C-shaped cavity divided into ()
- Body – at the parietal lobe
- Anterior horn – at the frontal lobe
- Posterior horn – at the occipital lobe
- Inferior horn – at the temporal lobe
Boundaries of the lateral ventricle – body
1) roof: undersurface of the corpus callosum
2) floor: body of the caudate nucleus & lateral margin of the thalamus
3) medial wall: septum pellucidum
Slit-like gap at the body of the ventricle where the choroid plexus projects into.
Through it, the blood vessels of the plexus invaginate the pia mater of the tela choroidea and the ependyma of the lateral ventricle
choroidal fissure
Boundaries of the lateral ventricle – anterior horn
1) roof: undersurface of the corpus callosum genu
2) floor: head of the caudate nucleus
3) medial wall: septum pellucidum and anterior column of the fornix
Boundaries of the lateral ventricle – posterior horn
1) roof: fibers of the tapetum of the corpus callosum
2) lateral wall: fibers of the optic radiation
3) medial wall: forceps major as the bulb of the posterior horn & calcarine sulcus as the calcar avis
Boundaries of the lateral ventricle – inferior horn
1) roof: tapetum of the corpus callosum and tail of the caudate nucleus
2) floor: collateral eminence of the collateral fissure, hippocampus
Is a vascular fringe composed of pia mater covered with the ependymal lining of the ventricular cavity;
projects into the ventricle on its medial aspect
choroid plexus
functions to produce CSF
slit-like cleft between 2 thalami
third ventricle
blood supply of the tela choroidea is derived from (1) and drains into (2)
(1) choroidal branches of the internal carotid and basilar arteries
(2) the internal cerebral veins > great cerebral vein
the layer of gray matter surrounding the cerebral aqueduct
central gray
the layer of gray matter surrounding the cerebral aqueduct
central gray
the layer of gray matter surrounding the cerebral aqueduct
central gray
(True/False)
The cerebral aqueduct does not have a choroid plexus
True
It is a ventricle situated anterior to the cerebellum and posterior to the pons and the superior half of the medulla oblongata
fourth ventricle
Boundaries of the 4th ventricle
1) cranial lateral: superior cerebellar peduncle
2) caudal lateral: inferior cerebellar peduncle
3) roof: superior medullary velum & inferior medullary velum
4) floor: posterior pons and superior medulla oblongata
4th ventricle communicates with the subarachnoid space through
at the inferior part of the roof
1) median aperture or foramen of Magendie
2) lateral openings of the fourth ventricle or foramina of Luschka
the openings permit CSF to flow from the ventricular system into the subarachnoid space
The diamond shaped floor of the fourth ventricle
formed by the posterior surface of the pons and the cranial half of the medulla oblongata
Rhomboid fossa
The floor is divided into symmetrical halves by the median sulcus
(from median sulcus towards lateral)
> medial eminence (elevation)
> sulcus limitans (sulcus)
> vestibular area
Slight swelling at the inferior end of the medial eminence of the fourth ventricle (floor)
produced by fibers from the motor nucleus of the facial nerve looping over the abducens nucleus
facial colliculus
A bluish gray area at athe superior end of the sulcus limitans
produced by a cluster of nerve cells containing melanin pigment
substantia ferruginea
Important structures at the fourth ventricle
(1) hypoglossal triangle - most medial, indicates the position of the underlying hypoglossal nucleus
(2) vagal triangle - beneath lies the dorsal motor nucleus of the vagus
(3) area postrema
Blood supply to the choroid plexus
posterior inferior cerebellar arteries
Space filled with csf and contains the large blood vessels of the brain
Subarachnoid space
Sites of CSF absorption
- arachnoid villi or arachnoid granulations that project into the dural venous sinuses
- directly into the veins in the subarachnoid space
- escapes through the perineural lymph vessesls
CSF absorption into venous sinuses occurs when CSF pressure exceeds the venous pressure in the sinus
Which vessels may be compressed in patients with raised CSF pressure as they cross the subarachnoid space around the optic nerve?
A. Central artery and vein of the retina
B. Ophthalmic artery and vein
C. Posterior ciliary arteries and veins
D. Optic artery and vein
Answer: A. Central artery and vein of the retina
A sleeve of the subarachnoid space extends around the optic nerve to the back of the eyeball
Here, the arachnoid mater and pia mater fuse with the sclera. The central artery and vein of the retina cross this extension of the subarachnoid space to enter the optic nerve, and they may be compressed in patients with raised CSF pressure.
(True/False)
The blood-brain-barrier (BBB) permeability is inversely related to the lipid solubility of a molecule and directly related to their size
False
BBB permeability is inversely related to the size of the molecules and directly related to their lipid solubility
- gases and water readily pass
- lipophilic molecules pass
- glucose and electrolytes pass slowly
- hydrophilic molecules do not pass
- plasma proteins and large organic molecules DO NOT PASS
Major structure responsible for BBB impermeability
tight junctions between the endothelial cells of blood capilliaries
BBB layers
- capillary lumen
(1) endothelial cells - connected by tight junctions
(2) cotinuous basement membrane
(3) foot processes of astrocytes
Blood-Cerebrospinal Fluid Barrier
Brain interfaces
